Management of semi-natural grasslands benefiting both plant and insect diversity: The importance of heterogeneity and tradition

Biodiversity of semi-natural grasslands depends on the management practices used. However, management systems suitable for one taxon, such as plants, can be detrimental to other taxa, such as insects, and vice versa. This study attempts to support conservation management planning by clarifying the effects of different grassland management practices on species richness and species composition of vascular plants, butterflies, moths, orthopterans and ground beetles, also taking into account the effects of climate and the landscape context. The study was performed in the White Carpathians Protected Landcape Area and UNESCO Biosphere Reserve (Czech Republic), which is famous for its grasslands with the globally highest fine-scale plant species richness. Different management practices (mowing, grazing, abandonment and mixed management; the latter including the previous three) were applied for at least five consecutive years at 34 sites, where plants and different insect groups were subsequently sampled. Effects of management on species richness of different taxonomic groups were assessed using generalised linear models, whereas the effects on species composition were assessed using redundancy analysis. Management influenced plant, butterfly and moth species richness, but the effects of particular management practices on all species and species of regional conservation importance differed between these taxonomic groups. Plant and moth species richness increased with mowing, but moth species richness decreased with grazing. Mixed management favoured plant and butterfly richness. Plant species composition was infuenced by mowing, grazing and mixed management while that of moths by mowing and grazing. Orthopterans and ground beetles did not respond significantly to management. Our results indicate that conservation management should comprise the traditional practices that have historically contributed to the formation of the biological diversity of the semi-natural grasslands in the study area. In particular, grazing may not be optimal for traditional hay-meadows and mowing should be carried out similarly as in pre-intensive farmland, creating spatio-temporal heterogeneity rather than uniformly cutting large grassland areas during a short period. In general, the optimal management should be heterogeneous, applying different practices in a mosaic or at different times during the season.